in reply to Printing out multiple array lists and more!

Since the lists are numeric, sorted and fairly small, a simple for loop works well. (Borrowing from mr. nick's code) 
#!/usr/local/bin/perl  
 
use strict; 
 
my $max = 0;

sub readfile { 
  my $fn=shift; 
  my @ar; 
 
  open IN,"<$fn" || die "Couldn't open '$fn': $!"; 
  ## snarf the header 
  scalar <IN>; 
  ## read the rest 
  while (<IN>) { 
    chomp; 
    push @ar,$_; 
    $max = $_ if $_ > $max;
  } 
  close IN; 

  @ar; 
} 
 

## load the files into arrays 
my @a=readfile 'f1.lst'; 
my @b=readfile 'f2.lst'; 
my @c=readfile 'f3.lst'; 
 
## iterate until all arrays are empty 
for (my $i = 0; $i <= $max; $i++)
{
  next unless $a[0] == $i || $b[0] == $i ||$c[0] == $i;
 
  ## print them out (if they match) 
  printf "%5s", $a[0]==$i ? scalar shift @a : undef; 
  print " | "; 
  printf "%5s", $b[0]==$i ? scalar shift @b : undef; 
  print " | "; 
  printf "%5s", $c[0]==$i ? scalar shift @c : undef; 
 
  print "\n"; 
}

[download]
This works on the lists you supplied. Brovnik.

Replies are listed 'Best First'.
Re: Re: Printing out multiple array lists and more!
by snafu (Chaplain) on May 17, 2001 at 22:00 UTC
    This worked perfectly!! I am studying the code right now. I understand the majority of it. I have one question though...

    Code for reference: 

          1 #!/usr/local/bin/perl
      2
      3 use strict;
      4
      5 my $max = 0;
      6
      7 sub readfile {
      8   my $fn=shift;
      9   my @ar;
     10
     11   open IN,"<$fn" || die "Couldn't open '$fn': $!";
     12   ## snarf the header
     13   scalar <IN>;
     14   ## read the rest
     15   while (<IN>) {
     16     chomp;
     17     push @ar,$_;
     18     $max = $_ if $_ > $max;
     19   }
     20   close IN;
     21
     22   @ar;
     23 }
     24
     25
     26 ## load the files into arrays
     27 my @a=readfile 'f1.lst';
     28 my @b=readfile 'f2.lst';
     29 my @c=readfile 'f3.lst';
     30
     31 ## iterate until all arrays are empty
     32 for (my $i = 0; $i <= $max; $i++)
     33 {
     34   next unless $a[0] == $i || $b[0] == $i || $c[0] == $i;
     35
     36   ## print them out (if they match)
     37   printf "%5s", $a[0]==$i ? scalar shift @a : undef;
     38   print " | ";
     39   printf "%5s", $b[0]==$i ? scalar shift @b : undef;
     40   print " | ";
     41   printf "%5s", $c[0]==$i ? scalar shift @c : undef;
     42
     43   print "\n";
     44 }

    [download]
    My only question is: In lines 36-41 you have a snippet  scalar shift @array. What is this doing? :) Thank you very much!!

    ----------
    - Jim

[reply]
[d/l]
[select]
      In my original code (which does not work for the test data :() I detected the end of the looping by testing to see if any of the arrays where still defined (had contents). Since I needed to pull the next number off the list to display it, I just combined a few operations from 
            if ($a[0]==$i) {
           printf "%5s",$a[0];
           shift @a;
      }

      [download]
      into the code you see. Oh, and I used scalar probably without need, but I wanted to make sure that the shift statement didn't pull off more than one element.
[reply]
[d/l]

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